BIS-DIOXOPIPERAZINE DERIVATIVES, PROCESS FOR THEIR PREPARATION, ANTITUMOR AGENTS COMPRISING THEM AND COMPOSITIONS CONTAINING THEM

BIS-DIOXOPIPERAZINE DERIVATIVES, PROCESS FOR THEIR PREPARATION, ANTITUMOR AGENTS COMPRISING THEM AND COMPOSITIONS CONTAINING THEM Disclosed are novel bis-dioxopiperazine derivatives and non-toxic salts thereof, process for their preparation, antitumor agents comprising them and compositions containing them. The bis-dioxopiperazine derivatives are represented by the following general formula (I): . . . . . (I) wherein R represents an alkyl radical having 1 to 17 carbon atoms, a cycloalkyl radical having 3 to 7 carbon atoms, a lower alkyl radical having a substituent or substituents selected from the group consisting of halogeno, carboxy, alkoxycarbonyl having 2 to 5 carbon atoms, lower alkoxy, substituted or unsubstituted phenoxy, naphthyloxy, substituted or unsubstituted phenylthio, substituted or unsubstituted phenyl and naphthyl, a substituted or unsubstituted phenyl lower alkenyl radical, a substituted or unsubstituted phenyl radical, a naphthyl radical, a heterocyclic radical selected from the group consisting of pyridyl, furyl and thienyl, an alkoxy radical having 1 to 8 carbon atoms, a substituted or unsubstituted phenyl lower alkoxy radical, or a substituted or unsubstituted phenoxy radical. A substituent or substituents on R may be selected from the group consisting of lower alkyl, halogeno, lower alkoxy, acyloxy having 2 to 5 carbon atoms, methylenedioxy, carboxy, amino, methanesulfonylamino and nitro. The above-mentioned "lower alkyl", "lower alkoxy" and "lower alkenyl" respectively refer to alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms and alkenyl having 2 to 4 carbon atoms.